Apparatus for indentation test and method for measuring mechanical properties using it

ABSTRACT

The present invention relates to an apparatus for indentation test, a method for measuring data of indentation test and mechanical properties using the apparatus, and recording means for storing the method for measuring mechanical properties. It relates to the apparatus for making the indentation testing continuously attached to the tested materials and evaluating tensile properties directly in field through analyzing the measured data using notebook computer connected to interface system, method for measuring data of indentation test and mechanical properties using the apparatus, and recording means for storing the method for measuring mechanical properties. The present invention provides an apparatus which is easily attached to the structures/facilities by miniaturizing of the apparatus and is used for materials irrespective of its size or kinds by adopting diversified attaching means for indentation test. It is not necessary to move the entire apparatus for testing multiple positions of the materials by adopting a horizontal moving means. Also the present invention provides an apparatus which can make cyclic loading and unloading, and measure the load and displacement data continuously, a method for measuring data of indentation test and mechanical properties using the apparatus, and recording means for storing the method for measuring mechanical properties. Also the present invention provides a method which measures mechanical properties saving testing costs and be used to acquire a test result in the case that it is difficult to obtain standard tensile testing specimens because it does not need separate tension tests for compensation of input experimental constants.

TECHNICAL FIELD

[0001] The present invention relates generally to an apparatus forindentation test, a method for measuring data of indentation test andmechanical properties using it, and recording means for storing themethod for measuring mechanical properties, and more particularly to anapparatus, a method and a recording means for the continuous indentationtesting for the materials and evaluating mechanical properties of thematerials such as tensile properties in field through analyzing themeasured data from the testing.

BACKGROUND OF THE INVENTION

[0002] The structural steels used to industrial structures/facilitieshave the problem that the reliability of the steels is declined as timepasses at the environmental condition of high pressure and temperature.Therefore it is necessary to develop non-destructive testing methodwhich can be used to evaluate the change of mechanical properties tofind out material degradation and particularly the mechanical propertiesof local weak region of the materials.

[0003] These requirements needed the means to measure tensile propertiesdirectly in field without preparing the test specimen with specifiedsize and tensile properties at the local region of the materials. Theapparatus for indentation test evaluating mechanical properties throughanalyzing indentation load-displacement curve from load and displacementdata obtained by indentation test is invented for these requirements.

[0004] In the field of indentation test, there is a patent entitled“Field indentation microprobe (FIM) for structural integrity evaluation(U.S. Pat. No. 4,852,397)”. But this invention requires the separatetension test for compensation of input experimental constant at theanalysis procedure of measured data to need extra cost, and if it isdifficult to obtain standard tension test specimen for the region ofmaterials this invention has a problem to evaluate tensile properties ofthe region of the materials.

[0005] Therefore, it is an object of the present invention to provide anapparatus which is easily attached to the structures/facilities byminiaturizing of the apparatus.

[0006] It is another object of the present invention to provide anapparatus that is used for materials irrespective of its size or kindsby adopting diversified attaching means for indentation test.

[0007] It is also another object of the present invention to move theentire apparatus for testing multiple positions of the materials byadopting a horizontal moving means.

[0008] It is still another object of the present invention to provide anapparatus which can make cyclic loading and unloading, and measure theload and displacement data continuously, a method for measuring data ofindentation test and mechanical properties using the apparatus, andrecording means for storing the method for measuring mechanicalproperties.

[0009] It is further another object of the present to provide a methodwhich measures mechanical properties saving testing costs and be used toacquire a test result in the case that it is difficult to obtainstandard tensile testing specimens because it does not need separatetension tests for compensation of input experimental constants.

BRIEF SUMMARY OF THE INVENTION

[0010] The present invention relates to an apparatus for indentationtest, a method for measuring data of indentation test and mechanicalproperties using the apparatus, and recording means for storing themethod for measuring mechanical properties. It relates to the apparatusfor making the indentation testing continuously attached to the testedmaterials and evaluating tensile properties directly in field throughanalyzing the measured data using notebook computer connected tointerface system, method for measuring data of indentation test andmechanical properties using the apparatus, and recording means forstoring the method for measuring mechanical properties.

[0011] The present invention provides an apparatus that is easilyattached to the structures/facilities by miniaturizing of the apparatusand is used for materials irrespective of its size or kinds by adoptingdiversified attaching means for indentation test. It is not necessary tomove the entire apparatus for testing multiple positions of thematerials by adopting a horizontal moving means.

[0012] Also the present invention provides an apparatus which can makecyclic loading and unloading, and measure the load and displacement datacontinuously, a method for measuring data of indentation test andmechanical properties using the apparatus, and recording means forstoring the method for measuring mechanical properties.

[0013] Also the present invention provides a method which measuresmechanical properties saving testing costs and be used to acquire a testresult in the case that it is difficult to obtain standard tensiletesting specimens because it does not need separate tension tests forcompensation of input experimental constants.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a schematic representation of the apparatus according toan embodiment of the present invention

[0015]FIG. 2 is a front cross-sectional view of the main body of FIG. 1.

[0016]FIG. 3 is a side cross-sectional view of the main body of FIG. 1.

[0017]FIG. 4 is a plane view including a part of cross-sectional view ofhorizontal moving means of FIG. 1.

[0018]FIG. 5 is a cross-sectional view of the lower part of main body,attaching means and specimen table of FIG. 1.

[0019]FIG. 6 is a flow chart of a method for measuring mechanicalproperties according to an embodiment of the present invention.

[0020]FIG. 7 is a flow chart of the step for selecting a method ofindenter moving of FIG. 6.

[0021]FIG. 8 is a flow chart of the step for indenter approaching thespecimen of FIG. 6.

[0022]FIG. 9 is a initial representation of recording means having amethod for measuring mechanical properties using the apparatus forindentation test.

[0023]FIG. 10 is a picture of setting up the experiment condition.

[0024]FIG. 11a is a picture of indentation load-displacement curvemeasured using the apparatus for indentation test according to anembodiment of the present invention.

[0025]FIG. 11b is a picture of indentation load-displacement curvesmeasured by a number of testing of same or different materials.

[0026]FIG. 12 is a graph of flow curve derived from indentationload-displacement curve of FIG. 11a.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0027] The present invention provides an apparatus for indentation test,which measures load and displacement of materials, connected to thecomputer having control program and mechanical properties analysisprogram by an interface board. It is composed of load applying meanswhich has load generating motor and reduction gear, load delivery meanswhich transform rotary power generated by load applying means to normalload, load sensing means which measures load continuously attached toload delivery means, connecting axis which moves in a same directionwith load sensing means connected to the end of load delivery means,indenter holder, indenter which is exposed at the end of indenter holderand applies contact load to materials, and displacement sensing meanswhich measure displacement continuously.

[0028] The present invention provides an apparatus for indentation testwhich has the space for connecting axis and indenter holder to movevertically, the base for supporting the components (hereinafter ‘mainbody’) at the bottom of the components, and additionally the attachingmeans which is connected to the base to fix the apparatus forindentation test into tested materials. The attaching means is one ofmagnet, chain, and U-block.

[0029] The present invention provides an apparatus for indentation testhaving horizontal moving means that can move only the main body withindenter in one horizontal direction while base and attaching means arefixed. The horizontal moving means has a slider base which has dovetailin upper surface and is connected to the base at the upper surface ofthe base, a slider which is positioned between the slider base and themain body and has dovetail groove for attaching to the dovetail ofslider base at the lower surface and screw groove made at the outersurface in the same direction with the dovetail groove, and a movinghandle which has two ends, of which one end is screwed with screw pitchat the groove of slider and the other end has a handle, and is screwedwith the base or the slider base by bracket between both ends.

[0030] The present invention provides an apparatus for indentation testincluding sensor for controlling indenter movement additionally thatsets up the limitation of the movement of the indenter for safety.

[0031] The present invention provides an apparatus for indentation testincluding the indenter whose shape is one type of ball, cone andsquare-pyramid And the indenter holder and the indenter is in one unitedbody.

[0032] Also, the present invention produces a method for measuring datausing the apparatus for indentation test comprising a step ofapproaching an indenter to materials; a step of load applying to set upthe loading rate and the indentation displacement, then to apply theindentation load to materials; a step of load removing for the indenterto move vertically as much as the indentation displacement, then to movevertically upward as much as the unloading ratio of the indentationdisplacement; a step of measuring the indentation load and theindentation displacement at the step for load applying and the step forload removal; a step of continuous testing to repeat the step of loadapplying, load removing and measuring; a step of removing the indenterfrom the materials.

[0033] The present invention provides a method to measure indentationdata using the apparatus for indentation test comprising a step ofapproaching an indenter to materials in which a step of moving indenterdownward and a step of deciding whether applied load is above ofpredetermined load or not are further included. If the applied load isabove predetermined load, then stop moving of the indenter and move theindenter upward as much as predetermined distance. If the applied loadis below predetermined load, then proceed to move the indenter downward.

[0034] The present invention provides a method to measure indentationdata using the apparatus for indentation test in which the predeterminedload is from 0.2 kgf to 2 kgf and the predetermined distance is from 5μm to 30 μm.

[0035] The present invention provides a method to measure indentationdata using the apparatus for indentation test in which one or more thanone of the loading rate, the indentation displacement and the unloadingratio can be changed at each continuous testing step.

[0036] The present invention provides a method to measure indentationdata using the apparatus for indentation test comprising a step ofapproaching the indenter to materials in which the indenter moves downto the starting point continuously if the indentation load is smallerthan the predetermined load, and the indenter stops and then moves up tothe predetermined distance if the indentation load reaches thepredetermined load; a step of load applying to set up the loading rateand the indentation displacement, then to apply the indentation load tomaterials; a step of load removing for the indenter to move verticallyas much as the indentation displacement, then to move vertically upwardas much as the unloading ratio of the indentation displacement; a stepof measuring the indentation load and the indentation displacement atthe step for load applying and the step for load removal; a step ofcontinuous testing to repeat the step of load applying, load removingand measuring; a step of removing the indenter from the materials; astep of calculating mechanical properties using stress-strain curvesderived from curves of indentation load-displacement measured at themeasuring step before and after the step of removing the indenter.

[0037] The present invention provides a method to measure indentationdata using the apparatus for indentation test additionally comprising astep of calculating the material properties by averaging the calculatedproperties obtained by repeating the procedures at the several uniaxiallocations of the same materials by moving only the frame including theindenter without moving the base or the attaching means of the apparatusfor indentation test.

[0038] The present invention provides a recording means for storing amethod for measuring mechanical properties using the apparatus forindentation test, comprising means of approaching the indenter tomaterials in which the indenter moves down to the starting pointcontinuously if the indentation load is smaller than the predeterminedload, and the indenter stops and then moves up to the predetermineddistance if the indentation load reaches the predetermined load; meansof load applying to set up the loading rate and the indentationdisplacement, then to apply the indentation load to materials; means ofload removing for the indenter to move vertically as much as theindentation displacement, then to move vertically upward as much as theunloading ratio of the indentation displacement; means of measuring theindentation load and the indentation displacement at the step for loadapplying and the step for load removal; means of continuous testing torepeat the step of load applying, load removing and measuring; means ofremoving the indenter from the materials; means of calculatingmechanical properties using stress-strain curves derived from curves ofindentation load-displacement measured at the measuring step before andafter the step of removing the indenter.

[0039] Embodiments of the present invention will be described in detailreferring to the drawings. These embodiments are only examples of thepresent invention in order to explain the technological ideas of thepresent invention, and the present invention is not limited by theembodiments.

[0040] 1. The Apparatus for Indentation Test

[0041] Referring FIG. 1 through FIG. 5, an embodiment of the indentationapparatus in accordance with the present invention is explained.

[0042]FIG. 1 is a schematic representation of the apparatus according toan embodiment of the present invention and FIG. 2 is a frontcross-sectional view of the main body of FIG. 1 and FIG. 3 is a sidecross-sectional view of the main body of FIG. 1 and FIG. 4 is a planeview including a part of cross-sectional view of horizontal moving meansof FIG. 1 and FIG. 5 is a cross-sectional view of the lower part of themain body, the attaching means and the specimen table FIG. 1.

[0043] Referring to FIG. 1, the apparatus according to the presentinvention is basically comprised of the main body 100, the notebookcomputer 200 connected to the main body 100 and the interface board 300which connects the main body 100 to the notebook computer 200.

[0044] The main body 100 is the main part of the apparatus forperforming the indentation tests, which attached to the materials to betested. The notebook computer 200 controls the main body 100 andcontains the program to analyze the data obtained from measuringmechanical properties by the main body 100. The interface board 300 isthe means to convert the signals between the main body 100 and thenotebook computer 200. The connectors included in the main body 100 andthe notebook computer 200 are connected to the connectors of theinterface board 300.

[0045] Referring to FIG. 2 and FIG. 3, the main body includes the frame101, the load applying means 110, the cylinder 121, the load sensingmeans 123, the indenter holder 125, the indenter 127, the displacementsensing means 128, the horizontal moving means 140, the sensing meansfor controlling indenter movement 151 and the connectors of the mainbody 161, 163, 165.

[0046] The frame 101 is a cylindrical case to protect the innercomponents. The frame 101 includes the load applying means 110, thecylinder 121, the load sensing means 123 and the part of the indenter127. It is easy to transport and carry the frame 101 because it is madeof ultra-light aluminum alloy.

[0047] The load applying means 110 generates the load applied to testmaterials for the indentation testing. The load applying means 110 iscomposed of the motor 111, the reduction gear 112 and the ball screw117. The motor 111 is the AC servo motor which is stable for overloadingand is controlled precisely, and that eliminates the effects of outsideparameters in-field such as vibration. The reduction gear 112 is locatedbelow the motor 111, and reduces the speed of the indenter 127 suitablefor the tests when the power generated by the motor 111 is transportedto the indenter 127. The coupling 113 located below the reduction gear112 connects the connecting axis 114 which is connected to the reductiongear 112 and the ball screw 117, and transport the power generated bythe motor 111 to the connecting axis 114. The bearings 115 locatedaround the connecting axis 114 supports the rotation movement of theconnecting axis 114. The supporting axis 116 penetrating the cylinder121 guides the movement of the cylinder 121, prevents the vibration ofthe cylinder 121, and protects the cylinder 121 from the possible shockwhen the cylinder 121 moves up and down. The ball screw 117 is rotatedby the power generated by the motor 111, and applies the load to theload sensing means 123. The ball screw nut 118 is combined with the ballscrew 117 using the screw pitch. Thus, the ball screws nut 118 moves upand down vertically when the ball screws 117 rotates.

[0048] The cylinder 121 converts the rotary power generated by the loadapplying means 110 to the vertical load and makes the indenter 127 applythe load to the tested materials because the cylinder 121 iscompressively combined with the ball screw nut 118. The cylinder 121 ispenetrated by the supporting axis 116 as explained above.

[0049] The cylinder 121 and the screw 123 a connect the load sensingmeans 123 located below the cylinder 121, and continuously measures theload applied by the cylinder 121. When the load sensing means 123 isindented, the deformation proportional to the applied load makes theresistance of deformation gauge in the load sensing means 123 changed,and finally the applied load can be measured continuously by measuringthe changed current. The maximum capacity of the load sensing means 123is 300 kgf and the load resolution is 0.3 kgf. Because the excessivemaximum capacity of the load sensing means 123 makes it difficult toprecisely analyze the data and the insufficient maximum capacity makesit difficult to obtain enough data, the optimum maximum capacity isdetermined by the various experiments.

[0050] The extension axis 124 located below the load sensing means 123connects the ball screw 117 and the indenter 127. The male screw made atthe upper end of the extension axis 124 is combined with the femalescrew made at the lower end of the load sensing means 123.

[0051] The indenter holder 125 and the indenter 127 are located at theend of the extension axis. The indenter 127 that applies contact load tothe tested materials is spherical. The indenter holder 125 and theindenter 127 are combined in one unit (that means it is not divided) andthe indenter 127 is formed at the end of the indenter holder 125. As theindenter holder 125 and the indenter 127 composes one unit, theseparation of the indenter 127 from the indenter holder 125 caused bydamage of the indenter holder 125 can be avoided and the experimentalerror caused by division of the indenter holder 125 and the indenter 127can also be avoided. The indenter 127 is a type of spherical, cone orsquare-pyramid according to applications. In certain circumstances, theindenter holder 125 and the indenter 127 can be divided.

[0052] The displacement sensing means 128 is located below the connector128 a contacted with the indenter 127 in parallel. The displacementsensing means 128 can be inserted to inside groove formed at the lowerend of connector 128 a when force is applied and it can be restored toinitial position by elastic assistant material that is installed ininside groove when force is removed. The sensor bracket 129 associatesthe connecting axis 124 which is connected to the indenter 127 with theconnector 128 a which is connected to the displacement sensing means128. When the indenter 127 is indented to the tested material, as thedisplacement sensing means 128 is inserted into the inside groove of theconnector 128 a and measures the depth of the insertion, the indentationdepth of the indenter 127 can be measured accordingly. The maximummeasurable displacement of the displacement sensing means 128 is 2 mmand LVDT (Linear Variable Displacement Transducer) is used for measuringthe accurate indentation depth but the displacement sensing means 128 isnot limited to LVDT.

[0053] Horizontal moving means 140 is located between the load sensingmeans 123 and the base 133. The horizontal moving means 140 is used formoving only the frame 101 horizontally, not moving the entire apparatuswhen other indentation test is conducted in other position of the sametested material after finishing one indentation test.

[0054] Referring to FIG. 2, FIG. 3 and mainly FIG. 4, the horizontalmoving means 140 which is located below the frame 101 of main body 100is composed of a slider 141, a slider base 142, a locking means 143, alocking means volt 143 a and a moving handle 145. The slider 141 islocated below the frame 101 of main body 100 and the slider base 142 islocated below the slider 141. Depressive dovetail groove 142 a is formedin the slider base 142 and prominent dovetail 141 b is formed in theslider 141. Both are fitted to each other. Therefore the slider 141 canslide along with the dovetail 141 b (or the dovetail groove 142 a)direction on the slider base 142 and make main body 100 movehorizontally. The locking means volt 143 a is cross-sectionallycontacted with the slide base 142 through the groove formed in theslider 141. As the locking means 143 is associated with the lockingmeans volt 143 a, rotation of the locking means 143 makes the lockingmeans volt 143 a move up and down. When the locking means 143 is rotatedfor extension of the locking means volt 143 a, it presses the sliderbase 142 to fix the slider 141. In this state when the locking means 143is rotated for shortening of the locking means volt 143 a, it releasesthe pressure to the slider base 142 and makes the slider 141 movehorizontally when force is applied to the slider 141. The moving handle145 generates the force making the slider 141 move horizontally. Thereare nut 145 c which is formed in the slider 141 through the bracket 145combined with volt 145 b. As the moving handle 145 is rotated, the voltof the moving handle 145 b is also rotated. The rotation of the volt ofthe moving handle 145 b makes the nut of the moving handle 145 c, theslider 141 and the frame 101 move to the direction or opposite directionof the moving handle 145 along with the direction of screw pitch. Thereare indicators that indicate the distance of movement is formed on themoving handle 145.

[0055] The sensing means for controlling indenter moving 151 is attachedto avoid the damage to apparatus that results from excessive upward ordownward movement of the indenter 127 and the displacement sensing means128. After the limit regions where the indenter 127 and the displacementsensing means 128 can move safely are defined, the sensing means forcontrolling indenter moving 151 is attached at the boundary of the limitregions respectively. The excessive movement of the indenter 127 and thedisplacement sensing means 128 outward boundary of the safe regionsmakes the rotation of motor stop resultantly to stop the movement of theindenter 127 and the displacement sensor 128.

[0056] Main body base 133 is located at the end of main body 100. Themain body base 133 connects the attaching means 130 with the main body100 or supports said main body 100 when the attaching means 133 is notinstalled.

[0057] Referring to FIG. 5, the apparatus for indentation test iscomposed of the main body 100 and also attaching means 130. Theattaching means 130 consists of magnet 131, magnetic bracket 131 a, twovolts 133 b, 133 b′. The magnetic bracket 131 a and the two volts 133 b,133 b′, connect the magnet 131 and the main body base 133 by screws. Themagnet 131 is used when object to which the apparatus is attached isiron and steel type material. The magnet 131 is used rounded form fittedto curvature in case the tested materials have curvature. Chain andU-block are also used along with the tested materials to which theapparatus is attached. Chain is used for wrapping the tested materialsfor attachment when the magnet 131 cannot be used. 4-lined chain is usedfor supporting large load up to 300 kg and it is connected to the mainbody base 133 by volts or screws. When U-block is used, brackets of bothsides are connected to U-block by volts to support the main body 100.

[0058] Referring to FIG. 1, main body connector that is located at thetop of the main body's frame 101 makes the main body 100 communicateswith interface board 300. The main body connector consists of motorconnector 161, encoder connector 163 and displacement connector 165which are respectively connected with motor connector 161′, encoderconnector 163′ and displacement connector 165′ of interface board 300.

[0059] Various properties of material such as hardness, flow curve,yield strength, work hardening index, tensile strength, non-uniformstrain etc. can be obtained at industrial sight by notebook computer inwhich program that analyzes indentation load applied to tested materialsand displacement data is embedded. The method of calculating aredescribed in Korean patent application 10-2001-1770 (The method ofcalculating of work hardening index and stress coefficient usingcontinuous indentation test), 10-2001-1771 (The method of calculating ofyield using continuous indentation test) and 10-2001-1772 (The method ofcalculating of tensile strength using continuous indentation test).

[0060] Also program embedded in notebook computer includes manualdriving function of motor for the approaching of the indenter to thetested material or for withdrawing and engage function of the indenterfor automatic positioning of the indenter to initial location ofindentation.

[0061] Referring to FIG. 1, motor connector 161′, encoder connector 163′and displacement connector 165′ which are respectively connected withmotor connector 161, encoder connector 163 and displacement connector165 of main body, are located in interface board 300. Also computerconnector 167 which is connected with communication port of notebookcomputer 200, UP/DOWN button 301 for manual movement of the indenter 127upward or downward, initializing button 303, emergency button 305 andpower button 307 are located in interface board 300.

[0062] Referring to FIG. 1,2,3,4 and 5, operation of the apparatus inaccordance with the invention is explained in detail as follows.

[0063] Firstly, attaching means 130 is attached to the testing materialafter attaching means 130 is combined with main body base 133 of mainbody by screws. Locking means 143 is rotated to move locking volt 143 adown to press slider base 142 for fixing of slider 141 and main body100. After pushing power button 307 of interface board 300 makes poweron, motor 111 is rotated by program embedded in notebook computer andthen reduction gear reduces the velocity which is suitable for thevelocity of the indenter 127 movement. Rotational force of motor 111rotates connecting axis 114 and the ball screw 117 and makes the ballscrew nut 118 move down vertically. The vertical movement of the ballscrew nut 118 makes the cylinder 121, load sensing means 123, theextension axis 123, the indenter holder 125 and the indenter 127 movedown simultaneously. At this time load sensing means 123 measures thechange of load continuously. Vertical load indents the indenter 127 tothe tested material. When the indentation depth increases by indentationof the indenter 127, displacement sensing means 128 is inserted into thegroove of the connector 128 a and measures load and the indentationdepth continuously along with the distance of insertion. The procedureof obtaining data of stress and strain by measuring load and theindentation depth and also by measuring load and the indentation depthupon removing of load applied to the indenter 127 to certain amount byrotating motor 111 in reverse direction by load sensing means 123 anddisplacement sensing means 128 is executed at one position. Again dataof stress and strain are obtained by measuring load and the indentationdepth continuously with applying load to the indenter 127 which makesthe indentation depth extended further and by removal of load applied tothe indenter 127 to certain amount. Repeating of the proceduresmentioned above can complete stress-stain curve at one position.

[0064] The same indentation test is executed in another test positionafter slider 141 moves horizontally by releasing the locking means 143of horizontal moving means 140 and rotating moving handle 145.

[0065] For the execution of the indentation test to another materials,after moving the indentation apparatus to another materials andattaching magnet 131 of attaching means to another materials isexecuted. Magnet can be formed curvature for the attachment to theobject that has curvature. If the object is not available for the use ofmagnet, other attaching means such as chain and U-block can be used forconnoting with main body base 133 after rotating volt 133 b whichconnects magnetic bracket 133 a of attaching means 130 and main bodybase 133 by screws to separate attaching means 130 from main body 100.

[0066] 2. The Method of Measuring Data and Calculating MechanicalProperties Using the Apparatus for Indentation Test

[0067] The methods of measuring data and calculating mechanicalproperties using the apparatus for indentation test are explained withreference to the FIG. 6 through FIG. 8 primarily, and FIG. 1 and FIG. 5additionally.

[0068]FIG. 6 is a flow chart of a method for measuring mechanicalproperties according to an embodiment of the present invention. FIG. 7is a flow chart of the step for selecting a method of indenter moving ofFIG. 6. FIG. 8 is a flow chart of the step for indenter approaching thespecimen of FIG. 6.

[0069] Referring to FIG. 6, measuring mechanical properties using theapparatus for indentation test according to the present inventioncomprises a step of selecting indenter moving method (S10), a step ofindenter approaching the specimen (sample material) (S20), a step ofload applying (S30), a step of unloading (S40), a step of measuringdisplacement (S50), a step of cyclic loading and unloading (S60), a stepof calculating of mechanical properties (S70), and a step of indenterwithdrawing (S80). The method for measuring data through indentationtest according to the present invention is measuring basic data forcalculating mechanical properties and is the same as the method ofmeasuring mechanical properties except not including a step ofcalculating mechanical properties (S70).

[0070] The step of selecting of indenter moving method (S10) isselecting whether to move an indenter (127) automatically or movemanually. Referring to FIG. 7, selection of indenter (127) moving methodis performed to make an indenter approach a sample, before execution ofindentation test is started (S10). Analysis program asks whether to movean indenter (127) manually and if yes, then loading rate is determined(S120). After setting up loading rate, pushing Up button (S130) makes anindenter (127) move upward (S150) and pushing Down button (S135) makesan indenter (127) move downward (S155).

[0071] In case of selecting to move an indenter (127) automatically(S115), moving speed of the indenter (127) has to be set up (S120′)anyway. Then input moving distance (S140), determine whether movingdistance is minus or not (S145). If moving distance is minus, move theindenter (127) upward (S150) and if moving distance is positive, movethe indenter downward (S155).

[0072] The step of indenter approaching the specimen (S20) is making anindenter (127) approaching the materials to start the indentation test.Referring to FIG. 8, displacement and load are indicated (S220) at realtime during the indenter (127) is moved downward (S210). Then theindenter's (127) bearing load is sensed whether it is over 1 kg or not(S230). If the load is over 1 kg (YES), the downward moving of theindenter (127) is stopped (S240) and moved 10 upward (S25) and stopped(S260). At this stage appropriate distance between the indenter (127)and the sample is set up for indentation test. If the indenter's bearingload is under 1 kgf (NO), the indenter (127) is moved downwardcontinuously until the load reaches 1 kgf and repeat the step forindenter approaching the specimen. The 1 kgf and 10 are the set up(predetermined) value of load and displacement respectively obtainedfrom repeated experiment. And measuring of mechanical properties is notaffected by this value because the range of data acquisition is over 1kgf. Also, though in this case set up (predetermined) value of load anddisplacement is 1 kgf and 10 respectively, the load and displacementvalue is available in the range between 0.2 2 kgf, 5 30 respectivelybased on the result of experiments. So this range of set up of engagingis included in the present invention.

[0073] The step of load applying (S30) is loading on the materials bydescending the indenter (127) vertically. Before this process the rateof vertical descent (moving rate) and the displacement of verticaldescent (moving displacement) is to be pre-set up. The rate anddisplacement can be obtained by controlling a motor (111) and areduction gear of the apparatus for indentation test. For example incase of maximum displacement is 300 and the number of sequence is 10,the rate is 0.1 mm/min and the displacement for one movement is be 30.

[0074] The step of unloading (S40) is moving the indenter (127) upwardby removing the load to a specific unloading ratio extent after theindenter (127) moved downward for the pre-set displacement. Controllinga motor (111) and a reduction gear of the apparatus for indentation testcan also operate this process. In this example if the unloading ratio is30%, the indenter is moved upward to the load of 70% of the load toobtain the displacement for one movement.

[0075] A step of measuring (S50) is measuring the indentationdisplacement and indentation load of the indenter (127) during the stepof load applying (S30) and the step of unloading (S40). This step (S50)is achieved by a displacement sensing means (128) and a load sensingmeans (123).

[0076] A step of cyclic loading and unloading (S60) is repeating thestep of load applying (S30) and the step of unloading (S40) to aspecific number of times. The moving rate, moving displacement, andunloading ratio can be set up (predetermined) differently at eachsequence. For example, high unloading ratio at early sequence of lowload (1 time through 3 times) and low unloading ratio as the sequenceincreases gradually cab be adopted. At early sequence, high unloadingratio reflects plastic deformation more precisely.

[0077] A step of calculating mechanical properties (S70) is as follows.Stress-strain curve is derived from indentation load-indentationdisplacement curve obtained in measuring step (S50). And mechanicalproperties are calculated using this stress-strain curve. Here,properties are flow curve, yield strength, strain-hardening exponent,tensile strength, Luders strain, etc. The method of calculating aredescribed in Korean patent application 10-2001-1770 (The method ofcalculating of work hardening index and stress coefficient usingcontinuous indentation test), 10-2001-1771 (The method of calculating ofyield using continuous indentation test) and 10-2001-1772 (The method ofcalculating of tensile strength using continuous indentation test).

[0078] A step of indenter withdrawing (S80) is withdrawing the indenter(127) from the materials. A step of calculating mechanical properties(S70) can be positioned before and after indenter withdrawing step(S80).

[0079] The method of measuring data and calculating mechanicalproperties using the apparatus for indentation test is explained abovewith reference to Figures, but present invention is not limited to theabove.

[0080] Using the horizontal moving means (140) of said apparatus, theindenter (127) can be moved to the direction of one axis horizontally.So by repeating said measuring method to the same sample, mechanicalproperties of the same sample can be obtained several times. Excludingtoo large or too small values from the results and averaging the restvalues can acquire more precise mechanical properties.

[0081] 3. The recording Means Storing Method for Measuring MechanicalProperties Using the Apparatus for Indentation Test.

[0082] The recording means storing method for measuring mechanicalproperties using the apparatus for indentation test (hereinafterreferred to as ‘recording means’) is explained with reference to FIG. 9through FIG. 12 primarily, FIG. 1 through FIG. 8 secondarily. Anarithmetic and control unit like computer can operate the recordingmeans. For example the recording means operated by notebook computer(200) in FIG. 1 controls the apparatus through the interface board(300), and outputs mechanical properties of materials based on measuredinput data from the apparatus.

[0083]FIG. 9 is a initial representation operated by computer ofrecording means having a method for measuring mechanical propertiesusing the apparatus for indentation test. FIG. 10 is a picture ofsetting up the experiment condition. FIG. 11a is a picture ofindentation load-displacement curve measured using the apparatus forindentation test according to an embodiment of the present invention.FIG. 11b is a picture of indentation load-displacement curves measuredby a number of testing of same or different materials. FIG. 12 is agraph of flow curve derived from indentation load-displacement curve ofFIG. 11a.

[0084] Referring to FIG. 9, the initial representation (picture) 400operated by computer comprises of upper menu 410, status menu ofapparatus 420, manual driving menu of motor 430, engage button 440,graph window 450, flow curve button 460, hardness analysis button 470.The menu of the initial picture can be operated by mouse or keyboard.

[0085] The upper menu 410 has basic menu such as a testing set up 410 a,port set up 410 b, and graph 410 c, etc. Selecting testing set up menu410 a, testing set up window is displayed. The testing set up includesthe kinds of indenter, the radius of indenter, times of multipleexperiments, maximum displacement, unloading ratio, time of load hold,etc. The final depth (displacement) and the loading rate (rate ofexperiment) can be controlled in the part of manual driving menu at thebottom. A schematic diagram is outputted according to these experimentalconditions and the estimated results according to these experimentalconditions is outputted.

[0086] The status menu of apparatus 420 displays present load anddisplacement of the indenter 127 in the apparatus.

[0087] The manual driving menu of motor 430 is used to approach theindenter 127 to sample materials before starting to test or withdraw theindenter 127 from sample materials to indent another position. Accordingto FIG. 7 after setting of moving speed of the indenter 127 (S120),pushing (S130) the ‘Up’ button of manual driving menu moves the indenter127 upward (S150). On the other hand, pushing the ‘Down’ button movesthe indenter 127 downward (S155).

[0088] Engage button 440 is the menu move the indenter 127 automaticallyto the position at which indentation test for sample materials ispossible without manually moving before starting of the test. Thiseliminates inconvenience that operator has to move indenter withobserving the indenter and sample manually. Referring to FIG. 8, pushingthe engage button 440 execute the step for indenter approaching thespecimen (sample materials)(S20) in FIG. 6, so that the indenter 127 islocated at appropriate point to test.

[0089] Pushing ‘Start’ button not described in the initial picture 400measures mechanical properties by executing the method stored in therecording means. Firstly, the process that present load and displacementof the indenter is displayed in the part of status menu of apparatus isexplained above. Also, indentation load curve to the cumulatedindentation displacement to the present state is displayed in the graphwindow 450 as represented in FIG. 11A. To obtain many indentation loadscurves to indentation displacement by indenting to the same samplethrough horizontal movement or to compare the change of tensileproperties according to the change of test point indentationload-indentation displacement curves can be overlapped as represented inFIG. 11B.

[0090] The initial picture 400 has a flow curve button 460 and ahardness analysis button 470. Pushing the flow curve button 460 displaysflow curve analysis window. In the flow curve analysis window, pushinganalysis start button derives flow curve. Also pushing the hardnessanalysis button 470 displays hardness curve analysis window and hardnessnumber is derived by pushing analysis start button. For example, pushingthe flow curve button 460 displays flow curve having strain as theabscissa and stress as the ordinate as represented in FIG. 12. Hollomonequation that optimizes strain-hardening behavior is expressed. Yieldstrength, tensile strength, strain-hardening exponent is expressed inFIG. 12. These contents can be saved using various file types, such asBMP.

[0091] The present invention provides an apparatus that is easilyattached to the structures/facilities by miniaturizing of the apparatus.

[0092] The present invention provides an apparatus that is used formaterials irrespective of its size or kinds by adopting diversifiedattaching means for indentation test.

[0093] The present invention does not need to move the entire apparatusfor testing multiple positions of the materials by adopting a horizontalmoving means.

[0094] The present invention provides an apparatus that can make cyclicloading and unloading, and measure the load and displacement datacontinuously to save testing time.

[0095] The present invention saves testing costs and is used to acquirea test result in the case that it is difficult to obtain standardtensile testing specimens because it does not need separate tensiontests for compensation of input experimental constants.

What is claimed is:
 1. An apparatus for indentation test which measuresload and displacement of sample materials, comprising: a load applyingmeans which generates load to be applied to said sample materials; aload delivery means that transform rotary power generated by said loadapplying means to vertical normal load associated with said loadapplying means; a load sensing means which measures load continuouslyattached to said load delivery means; a connecting axis that moves in asame direction with said load sensing means connected to the end of saidload delivery means; a indenting means that moves in a same directionwith said load sensing means connected to the end of said load deliverymeans and applies contact load to said sample materials; a displacementsensing means that measure indented displacement positioned in parallelwith said indenting means; a horizontal moving means that moves a mainbody with indenter attached to in one horizontal direction while saidsample materials is fixed.
 2. The apparatus for indentation test ofclaim 1, wherein said load applying means is comprised of a loadgenerating motor that generates load and a reduction gear that reducesthe speed of load applying.
 3. The apparatus for indentation test ofclaim 1, wherein said horizontal moving means has a slider base whichhas dovetail in upper, a slider which is positioned between the sliderbase and said main body and has dovetail groove for attaching to thedovetail of slider base at the lower surface and screw groove made atthe outer surface in the same direction with the dovetail groove, and amoving handle which has two ends, of which one end is screwed with screwpitch at the groove of slider and the other end has a handle.
 4. Theapparatus for indentation test of claim 1, further comprising; a basefor supporting the components of claim 1 at the bottom of saidcomponents; an attaching means which is connected to the base to fix theapparatus for indentation test into tested materials selected amongmagnet, chain, or U-block.
 5. The apparatus for indentation test ofclaim 1, wherein a horizontal moving means moves a main body withindenter attached to in one horizontal direction while said samplematerials, said base and said attaching means are fixed.
 6. Theapparatus for indentation test of claim 1, further comprising; a sensorfor controlling the movement of said indenter that sets up thelimitation of the movement of said indenter for safety to avoidexcessive upward or downward movement of said indenter and saiddisplacement sensing means attached at the boundary of the limitregions.
 7. A method for measuring data using an apparatus forindentation test comprising; a step of approaching an indenter to samplematerials; a step of setting up a loading rate and an indentationdisplacement, then applying an indentation load to said samplematerials; a step of unloading for said indenter to move vertically asmuch as an indented displacement, then to move vertically upward as muchas an unloading ratio of said indented displacement; a step of measuringsaid indentation load and said indented displacement at the step of loadapplying and the step of unloading; a step of continuous testing torepeat the step of said load applying, said unloading and saidmeasuring; a step of removing said indenter from said sample materials.8. An recording means for storing a method for measuring mechanicalproperties using the apparatus for indentation test, comprising; a meansfor approaching an indenter to sample materials in which said indentermoves down to a starting point if the indentation load is smaller thanthe predetermined load, and said indenter stops and then moves up to thepredetermined distance if an indentation load reaches the predeterminedload; a means for load applying to set up an loading rate and anindentation displacement, then to apply the indentation load tomaterials; a means for load removing for said indenter to movevertically as much as an indentation displacement, then to movevertically upward as much as the unloading ratio of said indentationdisplacement; a means for measuring said indentation load and saidindentation displacement at a step for load applying and a step for loadremoval; a means for continuous testing to repeat said step of loadapplying, load removing and measuring; a means for removing saidindenter from said sample materials; a means for calculating mechanicalproperties using stress-strain curves derived from curves of indentationload-displacement measured at said measuring step before and after saidstep of removing said indenter.